The Lyocell fiber (also named as solubility fiber), is a cellulose fabric that is obtained from wood pulp cellulose by an organic solvent spinning process, particularly is a regenerated fiber from solution of NMMO solvent with wood pulp cellulose by wet spinning method. In its process, the energy consumption is very low, the recovery rate of the NMMO solvent is over 99.5% for reuse, low toxicity without environmental pollution, the wastes are biodegradable in harmless and so like of advantages over the conventional colloid fiber so that it is called green fiber of the 21 century. Primitively, the process patent and product patent of the Lyocell fiber were granted to the German Akzo Nobel Company in 1978 and 1980 respectively. In 1989, the generic name “Lyocell fiber” was given by the international committee of artificial and synthetic fiber. Later on, it was successfully commercialized and marketed globally by the Courtaulds PLC of the United Kingdom (now known as Accordis Fibers) and the Austrian company Lenzing AG. Form the annual yield of 20 kilo-tons less up to over 200 kilo-tons nowadays with estimated expectation of 450 kilo-tons in 2010. Accordingly, the constant increment of the market share and influence of Lyocell fiber in the category of regenerated cellulose fiber is expectable in the future.
Moreover, due to excellent compatibility, the Lyocell fiber is easily blendless spun or blended with cotton, linen, silk, wool and synthetic fiber as well as colloid fiber to improve the fiber properties so that the fabrics from its yam has nice brilliance, softness, sleek, touch feeling and excellent suspension, air-permeability and wearing snugness. For pure Lyocell fabrics, owing to the pearl-like sheen, intrinsic fluid smoothness, aerial gauze-look and good suspension, various pure or blended dresses of different style are produced via diverse weaving and knitting technology such as high class jeans, women underwear and foundation garment, fashionable dress as well as men's high class shirt, recreational dress, casual dress and the like. For industrial application of the Lyocell fiber, its strength and dry tenacity is better than that of cotton and near to that of polyester, its moisture retention ability is approaching 90% dry tenacity, which is incomparable by other cellulose fibers. Therefore, the Lyocell fiber is widely applied in the non-woven, industrial filtering cloth, industrial filament and special paper. For instance, the Lyocell fiber can be fabricated via numerous technologies such as needle-punched method, hydro-entangled method, wet-laying method, dry-laying method and thermo-bonding method into various nonwovens with different feature, all of which are superior to the colloid fiber products. Besides, some European companies are researching on the application for the Lyocell fiber in the fields of sewing suture, fatigue clothes, protective clothes, diapers and medical clothes. Some Japanese paper manufacturers are researching on the special papers for specific usage.
Owing to the upsurge in the concept of environmental protection, the quality requirement in the clothes is accordingly promoted, the feature of antifungal, antibacteria and deodorant capability is most cared by the consumers especially. Examining the conventional process of the antibacteria fiber, most popular processes are “adding antibacteria agent method” and “fiber surface coating method”, both of which have common drawback of the weak persistence in the antibacteria effect resulting in derivatives of harmful substance.
Accordingly, biological improving methods are created such as Taiwan Invention Patent in number of 147162 with title of “processing method of fiber with feature of antifungal, antibacteria and deodorant capability”, which takes Lyocell fiber process in coordination with water soluble chitosan to produce fiber with feature of antifungal, antibacteria and deodorant capability. However, It is well known that chitin or chitosan is a linear poly-saccharide composed of randomly distributed β-(1-4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). The chitin substance is widely distributed in the nature, such as shells of shrimp and crab (refer to theses of scholars Lai/1979, Austin et al.,/1981 and Knorr/1984). For waste re-usage in food processing point, chitin and chitosan are worthy to develop and research.
Besides, the output quantity and value in the processing of shrimp and crab is the primary project of Taiwan aquatic products for a long time because valuable protein, astaxanthin and chitin abound in wastes of shrimp and crab, which becomes harmful burden to the ecological environment if being left alone and conversely becomes high value-added material if well processed for resulting in solving waste issue to produce economical benefit. Thus, multiple benefits can be obtained by innovative process (refer to the theses of scholars Chen and Zin/1995, Chen/1997). Moreover, 20%˜30% of chitin can be extracted from the shells of shrimp and crab by suitably purification process (refer to thesis of scholar Bough/1975). Various chitins of different degrees of deacetylation can be accomplished by thermal alkali treatment (refer to theses of scholars Knorr/1984, Grant et al.,/1988 and Lin/1992). The application field of the chitin/chitosan is widespread (refer to theses of scholars Muzzarelli/1977/1985, Knor/1984, Grant et al.,/1988, Sandford/1989, Lin/1992, Simpson et al.,/1994, Chen and Zin/1995, Chen/1997). Both of chitin and chitosan are environment-friendly with biodegradable and biocompatible features.
By perusal on the specifications and claims of Taiwan Invention Patent in number of 147162 with title of “processing method of fiber with feature of antifungal, antibacteria and deodorant capability”, we realize that the process procedure is in steps of adopting existing 20%˜30% chitin or chitosan extracted from shells of shrimp, crab and crustaceans in degree of deacetylation of 75%˜99% to mix with solution of NMMO and wood pulp in coordination with conventional Lyocell fiber process for forming dope via thermal stirring and blending, then to yield cellulose fiber with feature of antifungal, antibacteria and deodorant capability by conventional wet-sinning method. By further studying the experimental embodiments of foregoing patent, the degree of deacetylation for the selected chitosan must between 85%˜92%, the weight content percentage for the selected chitosan must be over 0.5% and the degree of polymerization for selected cellulose must be over 900 to yield cellulose fiber with feature of antifungal, antibacteria and deodorant capability. Therefore, if the degree of polymerization for selected cellulose is below 900, the cellulose will be unable to react with chitosan in complete solvation so that the expected feature of antifungal, antibacteria and deodorant capability is not achieved. Thus, for fiber of manufacturer in mass production, neither the selectable range in the degree of polymerization is acceptable nor the total processing cost is reasonable. By the same token, if the degree of deacetylation for the selected chitosan is beyond 85%˜92% or the weight content percentage is less than 0.5%, the expected feature of antifungal, antibacteria and deodorant capability is not achieved even the degree of polymerization for selected cellulose is over 900.
Regarding the recycling method of solvent recovery in the process, no concrete technical disclosure is expressed but casually mentions it by an ambiguous phrase of “general decompressed condensing method”, which is incomprehensible and doubtful to the people skilled in this field. Because the stain created by the thermal dissolution in the Lyocell fiber process will be dissolved in the water rinsing liquid, the processed solvent must be bleached before recovering procedure. Currently, hydrogen peroxide bleaching, active carbon bed absorption bleaching and sulfite bleaching are the three popular bleaching methods to be applied in different production scales. However, regardless either bleaching method being adopted, the cost for treating a great quantity water rinsing liquid used in the Lyocell fiber process will be innumerable. Thus, anyone of the foregoing three bleaching methods is practically inadequate from the economical viewpoint.
Besides, some filtration must be performed as some residues of active carbon and other impurities are contained in the water rinsing liquid after bleaching treatment aforesaid. Currently, frame-type filtrating machine, drum-type filtrating machine and bed-type filtrating machine are the three popular filtrating equipments to be adopted for treating these residues. For comprehensively considering all related factors such as equipment expense, filtrating speed and recovering quantity and the like, anyone of the foregoing three filtrating machines can not meet the requirement of the economical mass production. Moreover, as tiny quantity of NMMO is still remained in the water rinsing liquid after bleaching and filtrating treatments aforesaid, further refinement must be undertaken so that not only the consuming quantity of the solvent is decreased to minimum extent but also the quality of the recovered solvent is resumed to the original NMMO quality. All the conditions and issues mentioned above will happen in the process of mass production in association with the Taiwan Invention Patent in number of 147162 aforesaid, how can skip it over in perfunctory manner by only an ambiguous phrase of “general decompressed condensing method”?